PITTSBURGH - Leave it to a brainy Carnegie Mellon University professor to cook up a fun way to teach kids how many french fries they can eat.

Using cartoon characters named Elvis Pretzley, Fry Girls and Slop P. Joe, Kristin Hughes wants to spread the right word about nutrition and exercise: Just because Dad eats a huge plate of macaroni and cheese doesn't mean you have to imitate him.

"Not everyone has to eat the same portion size," said Hughes, an associate professor in Carnegie-Mellon's School of Design. "A lot of kids at this age, they get fed adult amounts . . . but everyone is really specific and individual. It's about my amount and no one else's amount."

When Hughes spent an afternoon at Pittsburgh Montessori School, a lively group of fifth graders gave high marks to her creation - a series of games called Fitwits.

Kathy Schwartz's students spent about an hour learning that Deep Dish Don (a slice of deep-dish pizza) likes to swim in grease, and that Mr. Leather (the popular fruit roll-ups) contains no real fruit. They gasped in disbelief when they heard the right portion of french fries should be no bigger than three fingers put together.

"Isn't that a bummer?" said Susan Fidler, a resident at the University of Pittsburgh Medical Center and part of a team working with Hughes.

Pittsburgh Montessori is one of five schools where Hughes and her partners are testing the games. The project developed about a year ago when Hughes received a $195,000 grant from the Heinz Endowments to help children learn about nutrition. She is collaborating with Ann McGaffey of UPMC St. Margaret Family Health Centers.

"What I love about it is that it takes important concepts in nutrition and makes them concrete," Fidler said.

A deck of oversized cards is modeled after the popular Memory game. The cards have pictures of foods such as broccoli, cheese and hamburgers. The goal is to pair them up with a card that shows the correct portion size: One thumb is the right serving size for peanut butter, one palm the right size for a piece of chicken, and so on.

Laurynn Morgan said she enjoyed the game, even if it meant she would have to cut back on favorite foods such as macaroni and cheese, chicken, and peach cobbler.

"I learned how to eat appropriately," said Morgan, 10. "I'll eat less portions. Well . . . I'll try."